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Re: Accessing a string from a display group.
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Re: Accessing a string from a display group.


  • Subject: Re: Accessing a string from a display group.
  • From: "Jerry W. Walker" <email@hidden>
  • Date: Wed, 11 Jan 2006 14:44:06 -0500

Hi, Matt,

On Jan 11, 2006, at 1:18 PM, Matt Harmon wrote:

Hi,
	Sorry for what I suspect is a basic question but I have seen no
examples in any of my week and a half of research.

It shouldn't be that hard. I've included some references below.

I've inherited a Web Objects application that uses display groups
for *everything* and I've been asked to make a change to the application
that requires my extracting data (strings) from a record that is currently
displayed in a display group.
The fetch specification for the display group appears to have been
created "codelessly" (that is, I can't seem to locate a reference to it
anywhere in the source code).

The display group was probably created by dragging an entity from the EOModel and dropping it on the WOComponent page in WOBuilder. You can confirm this by opening the WOComponent in WOBuilder that uses the display group. Look for the display group's name in WOBuilder's browser and if there's a check mark to the left of the display group's name, then the display group was created in this way and is automatically initialized.


If so, you will find the parameters for creating a fetch specification dynamically in the .woo file for that WOComponent. You can review the contents of the .woo file by clicking on the reveal triangle for the (yellow) group containing the WOComponent in Xcode's Groups and Files list, then clicking on the reveal triangle on the (blue) folder/directory for the WOComponent's package within the WOComponent's group.

You should see three files listed there with suffixes: .html, .wod, .woo. Click on the file with the .woo suffix and Xcode should show you a plist containing the initialization parameters for the WOComponent, which should include the initialization for the display group.

	How does one access a string (or any other variable for that matter)
in a display group that was created without code? Or do I just need to
rewrite the thing to do it all programmatically?

The best thing to do would probably be to learn about WODisplayGroups. It might be helpful to realize that they are little more than array controllers to provide a very convenient display control for arrays of EOs. If you try to learn about them knowing that this is their basic function, I think it's a bit easier. If you become their friend, your development life can generally get much easier (with minor caveats, but that's what the list is for) :-)


For your immediate problem, go to the WODisplayGroup JavaDocs. The display group is holding an array of EOs. You want to get to that array to manipulate its elements in some way. The array is given to you through the allObjects() method:

public NSArray allObjects()
Provides all of the objects collected by the WODisplayGroup. This collection differs from that provided by displayedObjects. Typically this collection will comprise the results of the last fetch from the WODisplayGroup's dataSource.


It's helpful to simply peruse the WODisplayGroup API page and the WODisplayGroup.Delegate Interface page, reviewing the members and methods described there.

Ravi Mendis introduces WODisplayGroups in his WO Developer's Guide on page 192. The discussion isn't very deep.

You can also get a free introduction to this useful topic at:

http://developer.apple.com/documentation/LegacyTechnologies/ WebObjects/WebObjects_4.5/System/Documentation/Developer/WebObjects/ Topics/TopicsTOC.html

Scan down the page to the heading: "Using Display Groups" and start reading the topics therein.

This material might be covered in a later version of WebObjects, but I know it's here and haven't time to look further.

In general, if your predecessor used display groups extensively on a project that you will be maintaining as you suggest, you will be far better off learning and working with his/her display groups, than you will be if you try to take it all back down to the code level.

Thanks for any information anyone can provide,
Matt Harmon

--
__ Jerry W. Walker,
WebObjects Developer/Instructor for High Performance Industrial Strength Internet Enabled Systems


    email@hidden
    203 278-4085        office



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 >Accessing a string from a display group. (From: "Matt Harmon" <email@hidden>)

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